SPEECHLESSLY
speechlessly
(adverb) without speaking; “he stood up soundlessly and speechlessly and glided across the hallway and through a door”
Source: WordNet® 3.1
Etymology
Adverb
speechlessly (comparative more speechlessly, superlative most speechlessly)
In a speechless manner; without speaking.
Source: Wiktionary
SPEECHLESS
Speech"less, a.
1. Destitute or deprived of the faculty of speech.
2. Not speaking for a time; dumb; mute; silent.
Speechless with wonder, and half dead with fear. Addison.
– Speech"less*ly, adv.
– Speech"less*ness, n.
Source: Webster’s Unabridged Dictionary 1913 Edition